Each of the strain ASL-7 and its parent strain ATCC14752 was cultured at 28° C. for 24 hours on the BYG agar medium. One loopful of the cultured cells were inoculated into a 300 ml capacity conical flask charged with 20 ml of a production medium (a medium prepared by dissolving 150 g of glucose, 50 g of ammonium chloride, 0.7 g of dipotassium hydrogenphosphate, 0.7 g of potassium dihydrogenphosphate, 0.5 g of magnesium sulfate heptahydrate, 20 mg of iron sulfate heptahydrate, 20 mg of manganese sulfate pentahydrate, 10 mg of zinc sulfate heptahydrate, 6 μg of biotin, 1 mg of thiamine hydrochloride and 5 g of meat extract in 1 liter of water, adjusting its pH to 7.2 and then adding 50 g of calcium carbonate thereto) and cultured at 28° C. for 96 hours.
